The present invention in general relates to a method and apparatus for filling fuel gas in a gas turbine. More particular, this invention relates to a method and apparatus for filling fuel gas in a gas turbine which can supply a predetermined fuel gas flow in accordance with the system state, by automatically changing open-close timings such as of a purge relief valve and a gas-filling opening of a main fuel valve, depending on an actual state of gas-filling, and by which adjustment work can be saved.
In a gas-fired gas turbine, it is necessary to perform a gas-filling process with respect to the fuel line (from a main fuel valve (or fuel gas supply valve) to a fuel shutoff valve) before the startup. This process is necessary, after a long-term shutdown of or inspection to the gas turbine where the fuel line should have been filled with an inert gas such as nitrogen, for replacement of the inert gas with a fuel gas at the startup to avoid supplying a combustor nozzle with mixture of fuel gas and inert gas, to thereby prevent a failure of light-up. The main fuel valve, to be open in usual run, should have a possibly reduced pressure loss, and hence a ball valve is employed therefore.
An automated unit for a series of sequential actions for such a gas-filling is adapted to simply open and close a main fuel valve (with a constant gas-filling opening) and a purge valve, with lapse of time. In a certain case, as the main fuel valve, there is employed no ball valve, but a dedicated valve apparatus that enables a delicate opening setting. However, such a case is out of the scope of the present invention.
A conventional automated gas-filling sequence performs mere opening and closing respectively of a main fuel valve (with a constant gas-filling opening) and a purge valve, with lapse of time (without feeding back a valve condition), so that the main fuel valve has an opening interval variable with associated system states (line length, diameter, configuration, etc.), resulting in troublesome on-site adjustment for setting the interval.
Moreover, the main fuel valve (ball valve) has an opening characteristic on which a delicate opening setting is difficult, and fails to follow a uniform gas-filling operation, due to different system states, such as inline temperature and pressure for gas-filling and flow characteristic of the main fuel valve, as another problem.
Further, the main fuel valve, which has difficulty with a delicate opening setting, causes a fuel gas to vigorously outflow when opened, with an impact that generates noises and may give damages to various devices.
Further, there is an associated tendency to release unburnt gases into the atmosphere until a predetermined time interval elapses, wasting fuel gas, which is non-economical, and unfavorable also in respect of environmental protection.
It is an object of the present invention to provide a method and apparatus for filling fuel gas in a gas turbine that is able, in a gas turbine plant provided with a fuel main valve comprised of a ball valve, to supply a predetermined gas flow in an adequate manner in accordance with a system state, thereby implementing adjustment labor saving and cost-down, noise reduction, reduction in degree of impact to a variety of devices, and the like.
The gas turbine fuel gas filling apparatus according to one aspect of this invention comprises a main fuel valve installed upstream of a fuel line and comprised of a ball valve, a fuel valve installed downstream of the fuel line and upstream of a combustor nozzle, an inert gas purge valve for purging out of the fuel line an inert gas supplied into the fuel line by a supply unit of the inert gas, and a pressure detector for detecting a pressure in the fuel line. Furthermore, the main fuel valve is gradually opened to be fixed to a valve opening at a time when a predetermined first pressure condition of the fuel line is established; after lapse of a predetermined time, again checking a state of pressure, the main fuel valve is gradually opened until a second pressure condition is established; the state of pressure is checked also upon a completion of gas-filling; the inert gas purge release valve is closed with establishment of a third pressure condition; and the main fuel valve is fully opened with establishment of a fourth pressure condition. A predetermined fuel gas flow is thereby adequately supplied to the fuel line in accordance with a system state.
Further, the number of times the pressure condition is set and the duration for which the measurement is performed are increased or decreased based on the system state.
The gas turbine fuel gas filling apparatus preferably further comprises a control valve for correcting a flow rate of gas outflowing from the main fuel valve in dependence on a state of temperature and pressure in the fuel line.
The gas turbine fuel gas filling apparatus preferably further comprises a combination of a bypass valve and an orifice for correcting a flow rate of gas outflowing from the main fuel valve in dependence on a state of temperature and pressure in the fuel line.
Furthermore, it is preferable that the fuel gas is natural gas.
Furthermore, it is preferable that the inert gas is nitrogen gas.
The method of filling fuel gas in a gas turbine, which gas turbine comprises a fuel line for supplying the fuel gas; a main fuel valve provided on the fuel line; a fuel valve provided on the fuel line on the downstream of the main fuel valve; a combustor nozzle as an outlet for the fuel gas; an inert gas supply for supplying an inert gas to the fuel line; an inert gas purge valve for purging out the inert gas out of the fuel line; and a pressure detector for detecting a pressure in the fuel line, according to another aspect of this invention comprises following steps.
1) Gradually opening the main fuel valve and simultaneously checking the pressure in the fuel line detected by the pressure detector.
2) Stopping opening of the main fuel valve when the pressure detected by the pressure detector has reached a predetermined first pressure.
3) Waiting for lapse of a predetermined time.
4) Checking the pressure in the fuel line detected by the pressure detector and determining whether the pressure detected by the pressure detector has reached a predetermined second pressure.
5) Gradually further opening the main fuel valve if the pressure detected by the pressure detector has not reached the second pressure.
6) Checking the pressure in the fuel line detected by the pressure detector and determining whether the pressure detected by the pressure detector has reached a predetermined third pressure.
7) Closing said inert gas purge release valve if the pressure detected by the pressure detector has reached the third pressure.
8) Checking the pressure in the fuel line detected by the pressure detector and determining whether the pressure detected by the pressure detector has reached a predetermined fourth pressure.
9) Fully opening the main fuel valve if the pressure detected by the pressure detector has reached the fourth pressure.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.